Frequency pre-compensation for high-speed train single frequency networks

ABSTRACT

Wireless communication devices, systems, and methods related to mechanisms for transmitting and receiving reference signals in a high-speed train (HST) single frequency network (SFN). A base station (BS) determines a first frequency pre-compensation value for a reference signal transmitted via a first transmission and reception point (TRP) and a second frequency pre-compensation value for a reference signal via a second TRP. The BS notifies a user equipment (UE) of the first and second pre-compensation values through at least one of the TRPs. The BS applies the first pre-compensation value to the reference signal via the first TRP and the second pre-compensation value to the reference signal via the second TRP. The UE adjusts its tracking loop for the reference signal based on the pre-compensation values, reducing estimation and/or search overhead at the UE.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and the benefit of U.S.Provisional Patent Application No. 63/008,562, filed Apr. 10, 2020, andentitled “Frequency Pre-Compensation for High-Speed Train SingleFrequency Networks,” the disclosure of which is incorporated byreference herein in its entirety as if fully set forth below in itsentirety and for all applicable purposes.

TECHNICAL FIELD

This application relates to wireless communication systems, and moreparticularly to methods (and associated devices and systems) forimproving communication in a high-speed train single frequency network.

INTRODUCTION

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing available systemresources. A wireless multiple-access communications system may includea number of base stations (BSs), each simultaneously supportingcommunications for multiple communication devices, which may beotherwise known as user equipment (UE). BSs may have numeroustransmission and reception points (TRPs, also known as remote radioheads (RRHs)) connected to them (e.g., via fiber), spaced at variouspoints distant from the BS to expand the coverage area outside the rangeof the BS itself.

Some TRPs may be located along the path of a high-speed train to enablecommunication between the BS and UEs located on the train duringtransit. The TRPs may operate using a single (common) frequency whencommunicating with a UE, making the existence of multiple TRPstransparent to the UE. As the UE moves at high velocity along therailway, the UE may receive signals from multiple TRPs at once andperform channel state estimation and provide channel state information(CSI) reports based on reference signals from multiple TRPs.

However, problems arise when transmitting and receiving referencesignals in the context of a rapidly-moving UE. As the UE moves rapidlytoward a TRP, the UE may perceive reference signals originating at theTRP at a higher frequency than expected because of the Doppler effect.Similarly, as the UE moves rapidly away from a TRP, the UE may perceivereference signals originating at the TRP at a lower frequency thanexpected because of the Doppler effect. If the Doppler shift becomes toogreat, i.e., greater than the pull-in range at the UE, the UE may beunable to acquire the reference signals transmitted from the TRP. Thus,there is a need to provide techniques for mitigating the effect of alarge Doppler shift in a high-speed train single frequency network toenable a UE to effectively receive reference signals from TRPs in thenetwork.

BRIEF SUMMARY OF SOME EXAMPLES

The following summarizes some aspects of the present disclosure toprovide a basic understanding of the discussed technology. This summaryis not an extensive overview of all contemplated features of thedisclosure and is intended neither to identify key or critical elementsof all aspects of the disclosure nor to delineate the scope of any orall aspects of the disclosure. Its sole purpose is to present someconcepts of one or more aspects of the disclosure in summary form as aprelude to the more detailed description that is presented later.

For example, in an aspect of the disclosure, a method of wirelesscommunication includes determining, by a base station, a frequencypre-compensation value for a transmission and reception point (TRP) on asingle frequency network (SFN). The method further includes indicating,by the base station to a user equipment (UE), the frequencypre-compensation value via the TRP. The method further includesapplying, by the base station, the frequency pre-compensation value to areference signal when directing the TRP to transmit the reference signalto the UE.

In an additional aspect of the disclosure, a method of wirelesscommunication includes receiving, by a user equipment from a TRP on anSFN, an indication of a frequency pre-compensation value for use by theTRP. The method further includes receiving, by the UE from the TRP, areference signal modified by the frequency pre-compensation value. Themethod further includes narrowing, by the UE, a range of a tracking loopbased on the indicated frequency pre-compensation value, and performing,by the UE, channel estimation based on the narrowed tracking loop.

In an additional aspect of the disclosure, a base station includes aprocessor configured to determine a frequency pre-compensation value fora TRP on an SFN. The processor is further configured to indicate to a UEthe frequency pre-compensation value via the TRP, and apply thefrequency pre-compensation value to a reference signal when directingthe TRP to transmit the reference signal to the UE.

In an additional aspect of the disclosure, a UE includes a transceiverconfigured to receive from a TRP on an SFN, an indication of a frequencypre-compensation value for use by the TRP. The transceiver is furtherconfigured to receive from the TRP a reference signal modified by thefrequency pre-compensation value. The UE also includes a processorconfigured to narrow range of a tracking loop based on the indicatedfrequency pre-compensation value and perform channel estimation based onthe narrowed tracking loop.

In an additional aspect of the disclosure, a non-transitorycomputer-readable medium has program code recorded thereon. The programcode includes code for causing a base station to determine a frequencypre-compensation value for a TRP on an SFN. The program code furtherincludes code for causing the base station to indicate to a UE thefrequency pre-compensation value via the TRP. The program code furtherincludes code for causing the base station to apply the frequencypre-compensation value to a reference signal when directing the TRP totransmit the reference signal to the UE.

In an additional aspect of the disclosure, a non-transitorycomputer-readable medium has program code recorded thereon. The programcode includes code for causing a UE to receive from a TRP on an SFN anindication of a frequency pre-compensation value for use by the TRP. Theprogram code further includes code for causing the UE to receive fromthe TRP a reference signal modified by the frequency pre-compensationvalue. The program code further includes code for causing the UE tonarrow a range of a tracking loop based on the indicated frequencypre-compensation value. The program code further includes code forcausing the UE to perform channel estimation based on the narrowedtracking loop.

In an additional aspect of the disclosure, a base station includes meansfor determining a frequency pre-compensation value for a TRP on an SFN.The base station further includes means for indicating to a UE thefrequency pre-compensation value via the TRP, and means for applying thefrequency pre-compensation value to a reference signal when directingthe TRP to transmit the reference signal to the UE.

In an additional aspect of the disclosure, a UE includes means forreceiving from a TRP on an SFN an indication of a frequencypre-compensation value for use by the TRP. The UE further includes meansfor receiving from the TRP a reference signal modified by the frequencypre-compensation value. The UE further includes means for narrowing arange of a tracking loop based on the indicated frequencypre-compensation value, and means for performing channel estimationbased on the narrowed tracking loop.

Other aspects, features, and embodiments of the present invention willbecome apparent to those of ordinary skill in the art, upon reviewingthe following description of specific, exemplary embodiments of thepresent invention in conjunction with the accompanying figures. Whilefeatures of the present invention may be discussed relative to certainembodiments and figures below, all embodiments of the present inventioncan include one or more of the advantageous features discussed herein.In other words, while one or more embodiments may be discussed as havingcertain advantageous features, one or more of such features may also beused in accordance with the various embodiments of the inventiondiscussed herein. In similar fashion, while exemplary embodiments may bediscussed below as device, system, or method embodiments, it should beunderstood that such exemplary embodiments can be implemented in variousdevices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication network according to someembodiments of the present disclosure.

FIG. 2 illustrates a high-speed train single frequency network accordingto embodiments of the present disclosure.

FIG. 3 illustrates a Doppler power spectral density according toembodiments of the present disclosure.

FIG. 4 illustrates a Doppler power spectral density according toembodiments of the present disclosure.

FIG. 5 is a block diagram of an exemplary UE according to embodiments ofthe present disclosure.

FIG. 6 is a block diagram of an exemplary BS according to embodiments ofthe present disclosure.

FIG. 7 illustrates a flow diagram of a wireless communication methodaccording to embodiments of the present disclosure.

FIG. 8 illustrates a flow diagram of a wireless communication methodaccording to embodiments of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with theappended drawings, is intended as a description of variousconfigurations and is not intended to represent the only configurationsin which the concepts described herein may be practiced. The detaileddescription includes specific details for the purpose of providing athorough understanding of the various concepts. However, it will beapparent to those skilled in the art that these concepts may bepracticed without these specific details. In some instances, well-knownstructures and components are shown in block diagram form in order toavoid obscuring such concepts.

This disclosure relates generally to wireless communications systems,also referred to as wireless communications networks. In variousembodiments, the techniques and apparatus may be used for wirelesscommunication networks such as code division multiple access (CDMA)networks, time division multiple access (TDMA) networks, frequencydivision multiple access (FDMA) networks, orthogonal FDMA (OFDMA)networks, single-carrier FDMA (SC-FDMA) networks, LTE networks, GlobalSystem for Mobile Communications (GSM) networks, 5^(th) Generation (5G)or new radio (NR) networks, as well as other communications networks. Asdescribed herein, the terms “networks” and “systems” may be usedinterchangeably.

An OFDMA network may implement a radio technology such as evolved UTRA(E-UTRA), Institute of Electrical and Electronics Engineers (IEEE)802.11, IEEE 802.16, IEEE 802.20, flash-OFDM and the like. UTRA, E-UTRA,and GSM are part of universal mobile telecommunication system (UMTS). Inparticular, long term evolution (LTE) is a release of UMTS that usesE-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in documentsprovided from an organization named “3rd Generation Partnership Project”(3GPP), and cdma2000 is described in documents from an organizationnamed “3rd Generation Partnership Project 2” (3GPP2). These variousradio technologies and standards are known or are being developed. Forexample, the 3rd Generation Partnership Project (3GPP) is acollaboration between groups of telecommunications associations thataims to define a globally applicable third generation (3G) mobile phonespecification. 3GPP long term evolution (LTE) is a 3GPP project whichwas aimed at improving the UMTS mobile phone standard. The 3GPP maydefine specifications for the next generation of mobile networks, mobilesystems, and mobile devices. The present disclosure is concerned withthe evolution of wireless technologies from LTE, 4G, 5G, NR, and beyondwith shared access to wireless spectrum between networks using acollection of new and different radio access technologies or radio airinterfaces.

In particular, 5G networks contemplate diverse deployments, diversespectrum, and diverse services and devices that may be implemented usingan OFDM-based unified, air interface. In order to achieve these goals,further enhancements to LTE and LTE-A are considered in addition todevelopment of the new radio technology for 5G NR networks. The 5G NRwill be capable of scaling to provide coverage (1) to a massive Internetof things (IoTs) with an ultra-high density (e.g., ˜1M nodes/km²),ultra-low complexity (e.g., ˜10 s of bits/sec), ultra-low energy (e.g.,˜10+ years of battery life), and deep coverage with the capability toreach challenging locations; (2) including mission-critical control withstrong security to safeguard sensitive personal, financial, orclassified information, ultra-high reliability (e.g., ˜99.9999%reliability), ultra-low latency (e.g., ˜1 ms), and users with wideranges of mobility or lack thereof; and (3) with enhanced mobilebroadband including extreme high capacity (e.g., ˜10 Tbps/km²), extremedata rates (e.g., multi-Gbps rate, 100+ Mbps user experienced rates),and deep awareness with advanced discovery and optimizations.

The 5G NR may be implemented to use optimized OFDM-based waveforms withscalable numerology and transmission time interval (TTI); having acommon, flexible framework to efficiently multiplex services andfeatures with a dynamic, low-latency time division duplex(TDD)/frequency division duplex (FDD) design; and with advanced wirelesstechnologies, such as massive multiple input, multiple output (MIMO),robust millimeter wave (mmWave) transmissions, advanced channel coding,and device-centric mobility. Scalability of the numerology in 5G NR,with scaling of subcarrier spacing, may efficiently address operatingdiverse services across diverse spectrum and diverse deployments. Forexample, in various outdoor and macro coverage deployments of less than3GHz FDD/TDD implementations, subcarrier spacing may occur with 15 kHz,for example over 5, 10, 20 MHz, and the like bandwidth (BW). For othervarious outdoor and small cell coverage deployments of TDD greater than3 GHz, subcarrier spacing may occur with 30 kHz over 80/100 MHz BW. Forother various indoor wideband implementations, using a TDD over theunlicensed portion of the 5 GHz band, the subcarrier spacing may occurwith 60 kHz over a 160 MHz BW. Finally, for various deploymentstransmitting with mmWave components at a TDD of 28 GHz, subcarrierspacing may occur with 120 kHz over a 500 MHz BW.

The scalable numerology of the 5G NR facilitates scalable TTI fordiverse latency and quality of service (QoS) requirements. For example,shorter TTI may be used for low latency and high reliability, whilelonger TTI may be used for higher spectral efficiency. The efficientmultiplexing of long and short TTIs to allow transmissions to start onsymbol boundaries. 5G NR also contemplates a self-contained integratedsubframe design with uplink/downlink scheduling information, data, andacknowledgement in the same subframe. The self-contained integratedsubframe supports communications in unlicensed or contention-basedshared spectrum, adaptive uplink/downlink that may be flexiblyconfigured on a per-cell basis to dynamically switch between uplink anddownlink to meet the current traffic needs.

Various other aspects and features of the disclosure are furtherdescribed below. It should be apparent that the teachings herein may beembodied in a wide variety of forms and that any specific structure,function, or both being disclosed herein is merely representative andnot limiting. Based on the teachings herein one of an ordinary level ofskill in the art should appreciate that an aspect disclosed herein maybe implemented independently of any other aspects and that two or moreof these aspects may be combined in various ways. For example, anapparatus may be implemented or a method may be practiced using anynumber of the aspects set forth herein. In addition, such an apparatusmay be implemented or such a method may be practiced using otherstructure, functionality, or structure and functionality in addition toor other than one or more of the aspects set forth herein. For example,a method may be implemented as part of a system, device, apparatus,and/or as instructions stored on a computer readable medium forexecution on a processor or computer. Furthermore, an aspect maycomprise at least one element of a claim.

The present disclosure describes mechanisms to better communicatereference signals in a high-speed train (HST) single frequency network(SFN) so that the effective Doppler spread of the reference signals arewithin the pull-in range of receiving user equipment (UEs). In an HSTSFN, a number of transmission and reception points (TRPs) aredistributed along the path of an HST. The TRPs are connected to one ormore base stations (BSs) through, for example, a fiber connection, andexpand the coverage area of the BS(s). As the train moves along thetrack, a UE on the train may transition its connection from a TRP it ismoving away from, to another TRP it is moving towards. A UE may beconnected to multiple TRPs at once. For example, each TRP may use thesame frequency for downlink communication to a UE so that the UE is onlyaware of a single TRP or BS, regardless of how many TRPs the UE isconnected to.

Each TRP may transmit a reference signal, e.g., a tracking referencesignal (TRS), which each TRP may have received from one or more BS(s).The TRS (which may also be a CSI-RS with TRS information) may indicateto the UE the Quasi-Colocation (QCL) type, which may indicate, forexample, Doppler shift, Doppler spread, average delay, and/or delayspread. Each TRS may be associated with a Transmission ConfigurationIndicator (TCI) state, from which the UE may derive time, frequency,and/or spatial properties of a signal for use in demodulating data(e.g., on the physical downlink shared channel) quasi-colocated with thereference signal. For example, a given BS may control multiple TRPsalong the path of the track. The BS may determine a TRS with a first TCIfor a first TRP and a second TRS with a second TCI for a second TRP. TheBS may derive a third TRS (e.g., from the first and second TRSs) with athird TCI state, with each TRP transmitting the third TRS on the SFN.The existence of the two distinct TRPs may remain invisible to the UEwhen using SFN, since both TRPs transmit the TRS on the sametime/frequency resources.

A channel in an HST SFN may possess different characteristics than achannel used for communication between a BS (or TRP) and a UE which isstationary or moving slower than an HST. An HST SFN channel undergoes ahigher Doppler shift and is highly direction (i.e., line-of-sightdominant), with low frequency selectivity. An HST SFN channel may alsohave a narrow Doppler spread (e.g., a maximum of about 13.9 kHz at 30GHz for a UE travelling at 500 km/h). Existing TRS schemes in FrequencyRange 2 (which includes millimeter wave frequencies) may have a pull-inrange of about ±14 kHz. Because the effective Doppler spread in an HSTSFN channel may be too large in relation to the pull-in range possibleat the UE, existing TRS schemes may not allow a UE to acquire TRSs fromTRPs in the HST SFN without prohibitive search overhead at the UE.According the aspects of the present disclosure, however, a BS may applyfrequency pre-compensation to the transmission of the TRSs on a per-beamor per-panel basis (or also, possibly, on a per-TRP basis) to alloweffective use of existing TRS structures in an HST SFN.

In some embodiments, a BS may determine a first frequencypre-compensation value for a first TRP in an HST SFN to apply whentransmitting the TRS to a UE. The BS may also determine a secondfrequency pre-compensation value for a second TRP to apply whentransmitting the TRS to the UE. The first and second pre-compensationvalues may be the same, or may be different from each other. Forexample, if the UE is travelling away from the first TRP and toward thesecond TRP, the pre-compensation value for the first TRP may be positive(i.e., the first TRP would increase the frequency at which the TRS istransmitted), and the pre-compensation value for the second TRP may benegative (i.e., the second TRP would decrease the frequency at which theTRS is transmitted). Each TRP may apply its respective pre-compensationvalue on a per-beam or per-panel basis (or, alternatively, per-TRPbasis). For example, different beams originating at a TRP may employdifferent pre-compensation values, and beams originating from differentpanels on the same TRP may employ different pre-compensation values. Thepre-compensation values may be arbitrary under the current operatingconditions, or selected from a set of candidate values.

In some embodiments, the BS may indicate the first and/or secondpre-compensation value to the UE, for example, in a downlink controlinformation (DCI) message or a radio resource control (RRC) signalthrough the first and/or second TRPs. The indication may be in the formof an index into a look-up table pre-configured on the UE. The UE mayuse the pre-compensation value(s) to inform its search for the TRS. Forexample, the UE may narrow the range of the tracking loop used toacquire the TRS based on the pre-compensation value(s). The UE may thenacquire the TRS and perform channel estimation based on the narrowedtracking loop range.

In some embodiments, the pre-compensation value(s) may be based on thecurrent properties of the SFN (e.g., on properties of the UE or theTRPs) and/or updated based on changes to the SFN. For example, thepre-compensation value(s) may be based on the position and velocity ofthe UE, which may be reported by the UE (e.g., based on GPS) ordetermined by the BS. The pre-compensation values may also be based on,for example, the beams and/or panels used by the first and/or secondTRPs to transmit the TRS. The pre-compensation value(s) may be updatedany time the SFN undergoes a change, and the new values may be appliedto the TRS by the respective TRPs and indicated to the UE.

In some embodiments, the BS may additionally or alternatively determinefrequency pre-compensation values and apply them to other types ofsignals (e.g., synchronization signals, signals carrying systeminformation, and/or synchronization signal blocks) as described hereinwith respect to reference signals. For example, primary synchronizationand/or secondary synchronization signals may also be frequencypre-compensated on a per-beam, per-panel, or per-TRP basis to enablemeaningful reception by the UE (as discussed with respect to the otherembodiments herein). Moreover, the coarse-level pre-adjustment may beconveyed as system information.

Aspects of the present application provide several benefits. Forexample, embodiments of the present disclosure allow a UE to betteracquire a TRS in an HST SFN by reducing the effective Doppler spread ofthe TRS. Narrowing the effective Doppler spread of the TRS (hencenarrowing the UE's tracking loop) also reduces the search and processingoverhead involved in locating the TRS.

FIG. 1 illustrates a wireless communication network 100 according tosome embodiments of the present disclosure. The network 100 may be a 5Gnetwork. The network 100 includes a number of base stations (BSs) 105(individually labeled as 105 a, 105 b, 105 c, 105 d, 105 e, and 105 f)and other network entities. A BS 105 may be a station that communicateswith UEs 115 and may also be referred to as an evolved node B (eNB), anext generation eNB (gNB), an access point, and the like. Each BS 105may provide communication coverage for a particular geographic area. In3GPP, the term “cell” may refer to this particular geographic coveragearea of a BS 105 and/or a BS subsystem serving the coverage area,depending on the context in which the term is used.

A BS 105 may provide communication coverage for a macro cell or a smallcell, such as a pico cell or a femto cell, and/or other types of cell. Amacro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEswith service subscriptions with the network provider. A small cell, suchas a pico cell, would generally cover a relatively smaller geographicarea and may allow unrestricted access by UEs with service subscriptionswith the network provider. A small cell, such as a femto cell, wouldalso generally cover a relatively small geographic area (e.g., a home)and, in addition to unrestricted access, may also provide restrictedaccess by UEs having an association with the femto cell (e.g., UEs in aclosed subscriber group (CSG), UEs for users in the home, and the like).A BS for a macro cell may be referred to as a macro BS. A BS for a smallcell may be referred to as a small cell BS, a pico BS, a femto BS or ahome BS. In the example shown in FIG. 1, the BSs 105 d and 105 e may beregular macro BSs, while the BSs 105 a-105 c may be macro BSs enabledwith one of three dimension (3D), full dimension (FD), or massive MIMO.The BSs 105 a-105 c may take advantage of their higher dimension MIMOcapabilities to exploit 3D beamforming in both elevation and azimuthbeamforming to increase coverage and capacity. The BS 105 f may be asmall cell BS which may be a home node or portable access point. A BS105 may support one or multiple (e.g., two, three, four, and the like)cells.

The network 100 may support synchronous or asynchronous operation. Forsynchronous operation, the BSs may have similar frame timing, andtransmissions from different BSs may be approximately aligned in time.For asynchronous operation, the BSs may have different frame timing, andtransmissions from different BSs may not be aligned in time.

The UEs 115 are dispersed throughout the wireless network 100, and eachUE 115 may be stationary or mobile. A UE 115 may also be referred to asa terminal, a mobile station, a subscriber unit, a station, or the like.A UE 115 may be a cellular phone, a personal digital assistant (PDA), awireless modem, a wireless communication device, a handheld device, atablet computer, a laptop computer, a cordless phone, a wireless localloop (WLL) station, or the like. In one aspect, a UE 115 may be a devicethat includes a Universal Integrated Circuit Card (UICC). In anotheraspect, a UE may be a device that does not include a UICC. In someaspects, the UEs 115 that do not include UICCs may also be referred toas IoT devices or internet of everything (IoE) devices. The UEs 115a-115 d are examples of mobile smart phone-type devices accessingnetwork 100. A UE 115 may also be a machine specifically configured forconnected communication, including machine type communication (MTC),enhanced MTC (eMTC), narrowband IoT (NB-IoT) and the like. The UEs 115e-115 k are examples of various machines configured for communicationthat access the network 100. A UE 115 may be able to communicate withany type of the BSs, whether macro BS, small cell, or the like, as wellas in some embodiments with any type of other UE 115. In FIG. 1, alightning bolt (e.g., communication links) indicates wirelesstransmissions between a UE 115 and a serving BS 105, which is a BSdesignated to serve the UE 115 on the downlink and/or uplink, or desiredtransmission between BSs, and backhaul transmissions between BSs, orsidelink transmissions between UEs (or via UEs serving as relays toBSs).

In operation, the BSs 105 a-105 c may serve the UEs 115 a and 115 busing 3D beamforming and coordinated spatial techniques, such ascoordinated multipoint (CoMP) or multi-connectivity. The macro BS 105 dmay perform backhaul communications with the BSs 105 a-105 c, as well assmall cell, the BS 105 f. The macro BS 105 d may also transmitsmulticast services which are subscribed to and received by the UEs 115 cand 115 d. Such multicast services may include mobile television orstream video, or may include other services for providing communityinformation, such as weather emergencies or alerts, such as Amber alertsor gray alerts.

The BSs 105 may also communicate with a core network. The core networkmay provide user authentication, access authorization, tracking,Internet Protocol (IP) connectivity, and other access, routing, ormobility functions. At least some of the BSs 105 (e.g., which may be anexample of a gNB or an access node controller (ANC)) may interface withthe core network through backhaul links (e.g., NG-C, NG-U, etc.) and mayperform radio configuration and scheduling for communication with theUEs 115. In various examples, the BSs 105 may communicate, eitherdirectly or indirectly (e.g., through core network), with each otherover backhaul links (e.g., X1, X2, etc.), which may be wired or wirelesscommunication links.

The network 100 may also support mission critical communications withultra-reliable and redundant links for mission critical devices, such asthe UE 115 e, which may be a drone. Redundant communication links withthe UE 115 e may include links from the macro BSs 105 d and 105 e, aswell as links from the small cell BS 105 f. Other machine type devices,such as the UE 115 f (e.g., a thermometer), the UE 115 g (e.g., smartmeter), and UE 115 h (e.g., wearable device) may communicate through thenetwork 100 either directly with BSs, such as the small cell BS 105 f,and the macro BS 105 e, or in multi-hop configurations by communicatingwith another user device which relays its information to the network,such as the UE 115 f communicating temperature measurement informationto the smart meter, the UE 115 g, which is then reported to the networkthrough the small cell BS 105 f. The network 100 may also provideadditional network efficiency through dynamic, low-latency TDD/FDDcommunications, such as in a vehicle-to-vehicle (V2V) communication. Thenetwork 100 may also further provide additional network efficiencythrough other device-to-device communication such as via PC5 links orother sidelinks, including according to embodiments of the presentdisclosure.

In some implementations, the network 100 utilizes OFDM-based waveformsfor communications. An OFDM-based system may partition the system BWinto multiple (K) orthogonal subcarriers, which are also commonlyreferred to as subcarriers, tones, bins, or the like. Each subcarriermay be modulated with data. In some instances, the subcarrier spacingbetween adjacent subcarriers may be fixed, and the total number ofsubcarriers (K) may be dependent on the system BW. The system BW mayalso be partitioned into subbands. In other instances, the subcarrierspacing and/or the duration of TTIs may be scalable.

In an embodiment, the BSs 105 may assign or schedule transmissionresources (e.g., in the form of time-frequency resource blocks (RB)) fordownlink (DL) and uplink (UL) transmissions in the network 100. DLrefers to the transmission direction from a BS 105 to a UE 115, whereasUL refers to the transmission direction from a UE 115 to a BS 105. Thecommunication may be in the form of radio frames. A radio frame may bedivided into a plurality of subframes or slots, for example, about 10.Each slot may be further divided into mini-slots. In a FDD mode,simultaneous UL and DL transmissions may occur in different frequencybands. For example, each subframe includes a UL subframe in a ULfrequency band and a DL subframe in a DL frequency band. In a TDD mode,UL and DL transmissions occur at different time periods using the samefrequency band. For example, a subset of the subframes (e.g., DLsubframes) in a radio frame may be used for DL transmissions and anothersubset of the subframes (e.g., UL subframes) in the radio frame may beused for UL transmissions.

The DL subframes and the UL subframes may be further divided intoseveral regions. For example, each DL or UL subframe may havepre-defined regions for transmissions of reference signals, controlinformation, and data. Reference signals are predetermined signals thatfacilitate the communications between the BSs 105 and the UEs 115. Forexample, a reference signal may have a particular pilot pattern orstructure, where pilot tones may span across an operational BW orfrequency band, each positioned at a pre-defined time and a pre-definedfrequency. For example, a BS 105 may transmit cell specific referencesignals (CRSs) and/or channel state information—reference signals(CSI-RSs) to enable a UE 115 to estimate a DL channel. Similarly, a UE115 may transmit sounding reference signals (SRSs) to enable a BS 105 toestimate a UL channel Control information may include resourceassignments and protocol controls. Data may include protocol data and/oroperational data. In some embodiments, the BSs 105 and the UEs 115 maycommunicate using self-contained subframes. A self-contained subframemay include a portion for DL communication and a portion for ULcommunication. A self-contained subframe may be DL-centric orUL-centric. A DL-centric subframe may include a longer duration for DLcommunication than for UL communication. A UL-centric subframe mayinclude a longer duration for UL communication than for ULcommunication.

In an embodiment, the network 100 may be an NR network deployed over alicensed spectrum. The BSs 105 may transmit synchronization signals(e.g., including a primary synchronization signal (PSS) and a secondarysynchronization signal (SSS)) in the network 100 to facilitatesynchronization. The BSs 105 may broadcast system information associatedwith the network 100 (e.g., including a master information block (MIB),remaining system information (RMSI), and other system information (OSI))to facilitate initial network access. In some instances, the BSs 105 maybroadcast the PSS, the SSS, and/or the MIB in the form ofsynchronization signal block (SSBs) over a physical broadcast channel(PBCH) and may broadcast the RMSI and/or the OSI over a physicaldownlink shared channel (PDSCH). The BS 105 may determine and applybeam-specific and/or panel-specific frequency pre-compensation to theSSB (e.g., to the signals in the SSB) when transmitting the SSB througha TRP as described in detail herein with respect to reference signalsaccording to embodiments of the present disclosure.

In an embodiment, a UE 115 attempting to access the network 100 mayperform an initial cell search by detecting a PSS from a BS 105. The PSSmay enable synchronization of period timing and may indicate a physicallayer identity value. The UE 115 may then receive a SSS. The SSS mayenable radio frame synchronization, and may provide a cell identityvalue, which may be combined with the physical layer identity value toidentify the cell. The PSS and the SSS may be located in a centralportion of a carrier or any suitable frequencies within the carrier.

After receiving the PSS and SSS, the UE 115 may receive a MIB. The MIBmay include system information for initial network access and schedulinginformation for RMSI and/or OSI. After decoding the MIB, the UE 115 mayreceive RMSI and/or OSI. The RMSI and/or OSI may include radio resourcecontrol (RRC) information related to random access channel (RACH)procedures, paging, control resource set (CORESET) for physical downlinkcontrol channel (PDCCH) monitoring, physical uplink control channel(PUCCH), physical uplink shared channel (PUSCH), power control, and SRS.

After obtaining the MIB, the RMSI and/or the OSI, the UE 115 may performa random access procedure to establish a connection with the BS 105. Ina four-step random access procedure, the UE 115 may transmit a randomaccess preamble and the BS 105 may respond with a random accessresponse. The random access response (RAR) may include a detected randomaccess preamble identifier (ID) corresponding to the random accesspreamble, timing advance (TA) information, a UL grant, a temporarycell-radio network temporary identifier (C-RNTI), and/or a backoffindicator. Upon receiving the random access response, the UE 115 maytransmit a connection request to the BS 105 and the BS 105 may respondwith a connection response. The connection response may indicate acontention resolution. In some examples, the random access preamble, theRAR, the connection request, and the connection response may be referredto as a message 1 (MSG 1), a message 2 (MSG 2), a message 3 (MSG 3), anda message 4 (MSG 4), respectively. In other examples, the random accessprocedure may be a two-step random access procedure, where the UE 115may transmit a random access preamble and a connection request in asingle transmission and the BS 105 may respond by transmitting a randomaccess response and a connection response in a single transmission. Thecombined random access preamble and connection request in the two-steprandom access procedure may be referred to as a message A (msgA). Thecombined random access response and connection response in the two-steprandom access procedure may be referred to as a message B (msgB).

After establishing a connection, the UE 115 and the BS 105 can enter anoperational state, where operational data may be exchanged. For example,the BS 105 may schedule the UE 115 for UL and/or DL communications. TheBS 105 may transmit UL and/or DL scheduling grants to the UE 115 via aPDCCH. The BS 105 may transmit a DL communication signal to the UE 115via a PDSCH according to a DL scheduling grant. The UE 115 may transmita UL communication signal to the BS 105 via a PUSCH and/or PUCCHaccording to a UL scheduling grant. Further, the UE 115 may transmit aUL communication signal to the BS 105 according to a configured grantscheme.

A configured grant transmission is an unscheduled transmission,performed on the channel without a UL grant. A configured grant ULtransmission may also be referred to as a grantless, grant-free, orautonomous transmission. In some examples, the UE 115 may transmit a ULresource via a configured grant. Additionally, configured-UL data mayalso be referred to as grantless UL data, grant-free UL data,unscheduled UL data, or autonomous UL (AUL) data. Additionally, aconfigured grant may also be referred to as a grant-free grant,unscheduled grant, or autonomous grant. The resources and otherparameters used by the UE for a configured grant transmission may beprovided by the BS in one or more of a RRC configuration or anactivation DCI, without an explicit grant for each UE transmission.Moreover, the UE may utilize a configured grant transmission in one ormore sidelink communications with one or more other UEs (either for D2Dcommunication or the other UE operating as an L2 or L3 relay to a BS).

The coverage range of a BS 105 can be extended by connecting one or moreTRPs 205 (as illustrated in FIG. 2) via, for example, a fiberconnection. A TRP 205 may itself be a BS 105. Alternatively, a TRP 205may include transmit functionality under the control of a remote BS 105,e.g. the TRP 205 may be an example of a remote radio head (RRH). A BS105 may communicate through one or more TRPs 205 with a UE 115. The BS105 may transmit data intended for the UE 115 to the TRP 205, which inturn may transit the data to the UE 115. Similarly, the UE 115 maytransmit a signal intended for a BS 105 to a TRP 205, which may thentransmit the signal to the BS 105.

FIG. 2 illustrates aspects of an HST SFN 200 according to embodiments ofthe present disclosure. For simplicity, a single BS 105 (or basebandunit), two TRPs 205, and one UE 115 are illustrated, but any fewer ormore than two TRPs 205 and more than one UE 115 are possible accordingto aspects of the present disclosure. BS 105 may rely upon one or moreof the TRPs 205 to communicate with the UE 115. In other examples, oneor more of TRPs 205 may be examples of BSs 105 in FIG. 1 (under controlof one or more BBUs).

A UE 115 traveling on a high-speed train (or at high speed generally)may quickly move out of the coverage range of a single BS 105. Toprovide connectivity to UE 115, a number of TRPs 205 may be connectedvia links 204 (e.g., fiber) to the BS 105 and placed at various pointsalong the path of a railway. For example, TRP 205 a is illustrated asconnected to BS 105 via link 204 a and TRP 205 b is connected to BS 105via link 204 b. As the UE 115 moves along the railway it may transitionbetween one or more TRPs 205. As illustrated, UE 115 may be in range ofand communicating with TRPs 205 a and 205 b. Each TRP 205 may transmit areference signal (e.g., a TRS) to UE 115. According to embodiments ofthe present disclosure, TRP 205 a may transmit TRS 206 a using a beam208 a and TRP 205 b may transmit TRS 206 b using a beam 208 b. While TRS206 a and TRS 206 b may be transmitted using distinct TCI states 1 and2, according to embodiments of the present disclosure, BS 105 may derivea single TRS appropriate for transmission from both TRSs 205 using TCIstate 3 with joint QCL data so that UE 115 is unaware it is receivingthe TRSs 206 (i.e., the same TRS) from two different TRPs 205. As UE 115moves away from TRP 205 a and toward TRP 205 b, the doppler effect maycause UE 115 to perceive TRS 206 a as being transmitted on a lowerfrequency than it is actually transmitted on, and TRS 206 b as beingtransmitted at a higher frequency than it is actually transmitted on.This may cause enough frequency shift that it falls outside the pull-inrange of the UE 115's tracking loop.

For example, turning now to FIGS. 3 and 4, FIG. 3 illustrates a Dopplerpower spectral density (PSD) model 300 for a signal (e.g., a TRS)transmitted from a single source (e.g., from a single TRP 205,originating at a BS 105, or from multiple TRPs 205 in an SFN) andreceived by a UE 115 according to aspects of the present disclosure. TheX-axis 302 represents the frequency shift from the carrier, and theY-axis 304 represents the Doppler PSD. F_(c) represents the central(expected) frequency, and F_(d) represents the maximum Doppler shift.Point 306 is the PSD at the central frequency (F_(c)), while point 308illustrates the PSD when the frequency is shifted downward by F_(d), andpoint 310 illustrates the PSD when the frequency is shifted upward byF_(d). The Doppler PSD model 300 is based on Clarke's model, whichassumes rich scattering around the UE's antenna upon reception. This maybe applicable in scenarios where the UE 115 is receiving signals in oneor more sub-6 GHz bands, and therefore lower Doppler shift (e.g., due tothe lower carrier frequency) with corresponding better pull-in range forthe UE 115's tracking loop.

By contrast, FIG. 4 illustrates the Doppler PSD in an HST SFN for asignal (e.g., a TRS) transmitted by two TRPs 205 (and originating at aBS 105) and received by a UE 115 where there is a larger Doppler shift(e.g., due to higher velocity and/or higher carrier frequency e.g. inthe mmW bands). Due to the high directionality of the beams(line-of-sight dominant) and low frequency selectivity, the Dopplerspread is narrower. Instead, it is Doppler shift dominant As a result ofthese characteristics, as illustrated there are effectively two copiesof the PSD curve, one centered at point 408 corresponding to thereceding TRP 205 (the TRP the UE is moving away from), and one centeredat point 410 corresponding to the TRP 205 the UE is moving toward. Dueto the high frequency and high speed, the Doppler spread is greater thanwhat is seen in FIG. 3. The larger Doppler spread in the HST SFNscenario of FIG. 4 makes it difficult for the UE 115 to receive the TRSusing existing TRS structures, without incurring significant search andprocessing overhead, and possibly renders the UE 115 unable to recoverthe TRS if the Doppler shift pushes the copies outside the pull-in rangeof the UE 115's tracking loop. According to embodiments of the presentdisclosure, the TRP(s) 205 may apply one or more frequencypre-compensation values before transmitting the TRSs so that they arewithin the pull-in range of the UE 115.

FIG. 5 is a block diagram of an exemplary UE 500 according toembodiments of the present disclosure. The UE 500 may be a UE 115 asdiscussed above in FIGS. 1-4. As shown, the UE 500 may include aprocessor 502, a memory 504, a frequency compensation module 508, atransceiver 510 including a modem subsystem 512 and a radio frequency(RF) unit 514, and one or more antennas 516. These elements may be indirect or indirect communication with each other, for example via one ormore buses.

The processor 502 may include a central processing unit (CPU), a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a controller, a field programmable gate array (FPGA) device,another hardware device, a firmware device, or any combination thereofconfigured to perform the operations described herein. The processor 502may also be implemented as a combination of computing devices, e.g., acombination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration.

The memory 504 may include a cache memory (e.g., a cache memory of theprocessor 502), random access memory (RAM), magnetoresistive RAM (MRAM),read-only memory (ROM), programmable read-only memory (PROM), erasableprogrammable read only memory (EPROM), electrically erasableprogrammable read only memory (EEPROM), flash memory, solid state memorydevice, hard disk drives, other forms of volatile and non-volatilememory, or a combination of different types of memory. In an embodiment,the memory 504 includes a non-transitory computer-readable medium. Thememory 504 may store, or have recorded thereon, instructions 506. Theinstructions 506 may include instructions that, when executed by theprocessor 502, cause the processor 502 to perform the operationsdescribed herein with reference to the UEs 115 in connection withembodiments of the present disclosure, for example, aspects of FIGS. 1-4and 7-8. Instructions 506 may also be referred to as program code. Theprogram code may be for causing a wireless communication device (orspecific component(s) of the wireless communication device) to performthese operations, for example by causing one or more processors (such asprocessor 502) to control or command the wireless communication device(or specific component(s) of the wireless communication device) to doso. The terms “instructions” and “code” should be interpreted broadly toinclude any type of computer-readable statement(s). For example, theterms “instructions” and “code” may refer to one or more programs,routines, sub-routines, functions, procedures, etc. “Instructions” and“code” may include a single computer-readable statement or manycomputer-readable statements.

The frequency compensation module 508 may be implemented via hardware,software, or combinations thereof. For example, frequency compensationmodule 508 may be implemented as a processor, circuit, and/orinstructions 506 stored in the memory 504 and executed by the processor502. In some examples, the frequency compensation module 508 can beintegrated within the modem subsystem 512. For example, the frequencycompensation module 508 can be implemented by a combination of softwarecomponents (e.g., executed by a DSP or a general processor) and hardwarecomponents (e.g., logic gates and circuitry) within the modem subsystem512.

The frequency compensation module 508 may be used for various aspects ofthe present disclosure, for example, aspects of FIGS. 1-4 and 7-8. Thefrequency compensation module 508 is configured to communicate withother components of the UE 500 to recover a TRS originating at a BS 105and transmitted by one or more TRPs 205 in an HST SFN. The TRS may havea frequency pre-compensation value applied by one or more of the TRPs205. For example, considering only two TRPs 205 (though any number ofTRPs 205 are possible), the first TRP 205 may apply a firstpre-compensation value to the TRS, and the second TRP 205 may apply asecond pre-compensation value to the TRS (each before transmission). Thepre-compensation values may be the same, or different from each other.For example, if the UE 500 is travelling away from the first TRP 205 andtoward the second TRP 205, the frequency compensation module 508 mayrecover the TRS from the first TRP 205 after the first TRP 205 applied apositive pre-compensation value (i.e., at an increased frequency), andit may recover the TRS from the second TRP 205 after the second TRP 205applied a negative pre-compensation value (i.e., at a decreasedfrequency). The TRS may also or alternatively be transmitted ondifferent beams or from different panels on the TRPs 205, with the TRSoriginating at each beam or panel having a different frequencypre-compensation value applied.

According to embodiments of the present disclosure, the frequencycompensation module 508 may be able to recover the TRS because thepre-compensation values shift the TRSs to a range around the carrierfrequency that is within the tracking loop capability of the UE 500. Insome examples, the frequency compensation module 508 may have furtherstored the one or more pre-compensation values that the TRPs 205 willapply (e.g., received at a prior time via RRC and/or DCI signaling). Insuch examples, the frequency compensation module 508 may use as theinitial value for the frequency tracking loop the compensated frequencyper the corresponding beam/pane/TRP. The frequency compensation module508 may, in some examples, use an index signaled from the TRP(s) 205that identifies what entry to access within a look-up table that storesa plurality of pre-compensation values for the UE 500 to apply overtime.

According to embodiments of the present disclosure, the BS mayadditionally or alternatively determine frequency pre-compensationvalues and apply them to other types of signals (e.g., tosynchronization signals and signals carrying system information, or toSSBs) as described herein within to reference signals. For example,primary synchronization and/or secondary synchronization signals mayalso be frequency pre-compensated on a per-beam, per-panel, or per-TRP205 basis to enable meaningful reception by the UE 500 (as discussedwith respect to the other embodiments herein). Moreover, thecoarse-level pre-adjustment may be conveyed as system information. Thefrequency compensation module 508 would process such signals andinformation in similar manner as described above with respect to thereference signal examples.

As shown, the transceiver 510 may include the modem subsystem 512 andthe RF unit 514. The transceiver 510 can be configured to communicatebi-directionally with other devices, such as the BSs 105. The modemsubsystem 512 may be configured to modulate and/or encode the data fromthe memory 504, and/or the frequency compensation module 508 accordingto a modulation and coding scheme (MCS) (e.g., a low-density paritycheck (LDPC) coding scheme, a turbo coding scheme, a convolutionalcoding scheme, a digital beamforming scheme, etc.). The RF unit 514 maybe configured to process (e.g., perform analog to digital conversion ordigital to analog conversion, etc.) modulated/encoded data (e.g., ULdata bursts, RRC messages, configured grant transmissions, ACK/NACKs forDL data bursts) from the modem subsystem 512 (on outbound transmissions)or of transmissions originating from another source such as a UE 115 ora BS 105. The RF unit 514 may be further configured to perform analogbeamforming in conjunction with the digital beamforming. Although shownas integrated together in transceiver 510, the modem subsystem 512 andthe RF unit 514 may be separate devices that are coupled together at theUE 500 to enable the UE 500 to communicate with other devices.

The RF unit 514 may provide the modulated and/or processed data (e.g.,data packets or, more generally, data messages that may contain one ormore data packets and other information) to the antennas 516 fortransmission to one or more other devices. The antennas 516 may furtherreceive data messages transmitted from other devices. The antennas 516may provide the received data messages for processing and/ordemodulation at the transceiver 510. The transceiver 510 may provide thedemodulated and decoded data (e.g., system information message(s), RACHmessage(s) (e.g., DL/UL scheduling grants, DL data bursts, RRC messages,ACK/NACK requests, reference signals such as TRSs, etc.) to thefrequency compensation module 508 for processing. The antennas 516 mayinclude multiple antennas of similar or different designs in order tosustain multiple transmission links. The RF unit 514 may configure theantennas 516.

In an embodiment, the UE 500 can include multiple transceivers 510implementing different RATs (e.g., NR and LTE). In an embodiment, the UE500 can include a single transceiver 510 implementing multiple RATs(e.g., NR and LTE). In an embodiment, the transceiver 510 can includevarious components, where different combinations of components canimplement different RATs.

FIG. 6 is a block diagram of an exemplary BS 600 according toembodiments of the present disclosure. The BS 600 may be a BS 105 asdiscussed above in FIGS. 1-4. As shown, the BS 600 may include aprocessor 602, a memory 604, a frequency compensation module 608, atransceiver 610 including a modem subsystem 612 and a RF unit 614, andone or more antennas 616. These elements may be in direct or indirectcommunication with each other, for example via one or more buses.

The processor 602 may have various features as a specific-typeprocessor. For example, these may include a CPU, a DSP, an ASIC, acontroller, a FPGA device, another hardware device, a firmware device,or any combination thereof configured to perform the operationsdescribed herein. The processor 602 may also be implemented as acombination of computing devices, e.g., a combination of a DSP and amicroprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The memory 604 may include a cache memory (e.g., a cache memory of theprocessor 602), RAM, MRAM, ROM, PROM, EPROM, EEPROM, flash memory, asolid state memory device, one or more hard disk drives, memristor-basedarrays, other forms of volatile and non-volatile memory, or acombination of different types of memory. In some embodiments, thememory 604 may include a non-transitory computer-readable medium. Thememory 604 may store instructions 606. The instructions 606 may includeinstructions that, when executed by the processor 602, cause theprocessor 602 to perform operations described herein, for example,aspects of FIGS. 1-4 and 7-8. Instructions 606 may also be referred toas code, which may be interpreted broadly to include any type ofcomputer-readable statement(s) as discussed above with respect to FIG.5.

The frequency compensation module 608 may be implemented via hardware,software, or combinations thereof. For example, the frequencycompensation module 608 may be implemented as a processor, circuit,and/or instructions 606 stored in the memory 604 and executed by theprocessor 602. In some examples, the frequency compensation module 608can be integrated within the modem subsystem 612. For example, thefrequency compensation module 608 can be implemented by a combination ofsoftware components (e.g., executed by a DSP or a general processor) andhardware components (e.g., logic gates and circuitry) within the modemsubsystem 612.

The frequency compensation module 608 may be used for various aspects ofthe present disclosure, for example, aspects of FIGS. 1-4 and 7-8. Thefrequency compensation module 608 may be configured to communicate withother components of the BS 600 to help determine a TRS for transmissionto a UE 115 from one or more TRPs 205, and to help determine a frequencypre-compensation value for the TRPs 205 to apply when transmitting theTRS to the UE 115. For example, the frequency compensation module 608may be configured to determine a first frequency pre-compensation valuefor a first TRP in an HST SFN to apply to a TRS when transmitting theTRS to a UE. The frequency compensation module 608 may also beconfigured to determine a second frequency pre-compensation value for asecond TRP to apply to the TRS when transmitting the TRS to the UE. Thefirst and second pre-compensation values may be the same, or may bedifferent from each other. For example, if the UE is travelling awayfrom the first TRP 205 and toward the second TRP 205, thepre-compensation value for the first TRP 205 may be positive (i.e., thefirst TRP 205 would increase the frequency at which the TRS istransmitted), and the pre-compensation value for the second TRP 205 maybe negative (i.e., the second TRP 205 would decrease the frequency atwhich the TRS is transmitted). Each TRP 205 may apply its respectivepre-compensation value as determined by the frequency compensationmodule 608 on a per-beam or per-panel basis (or, alternatively, on aper-TRP basis). For example, different beams originating at a TRP 205may employ different pre-compensation values (e.g., even if from thesame panel), and beams originating from different panels on the same TRP205 may employ different pre-compensation values (i.e., multiple beamsfrom the same panel apply the same pre-compensation value, but differentfrom beams from other panels).

The frequency compensation module 608 may select pre-compensation valuesarbitrarily or select the pre-compensation values from a set ofcandidate values. In another example, the frequency compensation module608 may be configured to determine the pre-compensation value(s) basedon the current properties of the SFN (e.g., on properties of the UE 115or the TRPs 205) and/or update the pre-compensation value(s) based onchanges to the SFN. For example, the pre-compensation value(s) may bebased on the position and velocity of the UE 115, which may be reportedby the UE 115 (e.g., based on GPS) or determined (or estimated) by theBS 600. Or, the BS 600 may be in communication with an HST itself in theSFN to obtain current or future velocity information (and/or relatedposition information). The frequency compensation module 608 may alsodetermine the pre-compensation values based on, for example, the beamdirections used by the first and/or second TRPs to transmit the TRS. Thefrequency compensation module 608 may update the pre-compensationvalue(s) any time the SFN undergoes a change, and the new values may beapplied to the TRS by the respective TRPs 205.

In some embodiments, the frequency compensation module 608 may beconfigured to indicate the first and/or second pre-compensation value tothe UE 115 (e.g., in a downlink control information (DCI) or radioresource control (RRC) message) through the first and/or second TRPs205. The indication may be in the form of an index into a look-up tablepre-configured on the UE 115, for example. Further, in embodiments wherethe frequency compensation module 608 updates one or more of thepre-compensation values (e.g., based on a change in the SFN, detected orpredicted/estimated), the frequency compensation module 608 may causethe values to be indicated to the UE 115 (e.g., in a DCI message or anRRC message if for a longer time horizon, either with the value itselfbeing signaled or an index or other identifier that the UE 115 may useto locate the value).

In some embodiments, the UE may additionally or alternatively receiveother types of signals (e.g., synchronization signals and signalscarrying system information, and/or SSBs) with frequencypre-compensation applied as described herein with respect to referencesignals. The UE may also receive indications of the frequencypre-compensation applied to the other types of signals. For example,primary synchronization and/or secondary synchronization signals mayalso be frequency pre-compensated on a per-beam, per-panel, or per-TRP205 basis to enable meaningful reception by the UE 500 (as discussedwith respect to the other embodiments herein). Moreover, thecoarse-level pre-adjustment may be conveyed as system information. Thefrequency compensation module 608 would perform similar operations toachieve this in similar manner as described above with respect to thereference signal examples. As shown, the transceiver 610 may include themodem subsystem 612 and the RF unit 614. The transceiver 610 can beconfigured to communicate bi-directionally with other devices, such asthe UEs 115 and/or 300 and/or another core network element. The modemsubsystem 612 may be configured to modulate and/or encode data accordingto a MCS (e.g., a LDPC coding scheme, a turbo coding scheme, aconvolutional coding scheme, a digital beamforming scheme, etc.). The RFunit 614 may be configured to process (e.g., perform analog to digitalconversion or digital to analog conversion, etc.) modulated/encoded data(e.g., RRC messages, TRSs, etc.) from the modem subsystem 612 (onoutbound transmissions) or of transmissions originating from anothersource, such as a UE 115 or 300. The RF unit 614 may be furtherconfigured to perform analog beamforming in conjunction with the digitalbeamforming. Although shown as integrated together in transceiver 610,the modem subsystem 612 and/or the RF unit 614 may be separate devicesthat are coupled together at the BS 600 to enable the BS 600 tocommunicate with other devices.

The RF unit 614 may provide the modulated and/or processed data, (e.g.,data packets or, more generally, data messages that may contain one ormore data packets and other information) to the antennas 616 fortransmission to one or more other devices. The antennas 616 may furtherreceive data messages transmitted from other devices and provide thereceived data messages for processing and/or demodulation at thetransceiver 610. The transceiver 610 may provide the demodulated anddecoded data (e.g., RRC messages, UL data, information about a UE 500′sposition and velocity, etc.) to the frequency compensation module 608for processing. The antennas 616 may include multiple antennas ofsimilar or different designs in order to sustain multiple transmissionlinks.

In an embodiment, the BS 600 can include multiple transceivers 610implementing different RATs (e.g., NR and LTE). In an embodiment, the BS600 can include a single transceiver 610 implementing multiple RATs(e.g., NR and LTE). In an embodiment, the transceiver 610 can includevarious components, where different combinations of components canimplement different RATs.

FIG. 7 illustrates a flow diagram of a wireless communication method 700according to some embodiments of the present disclosure. Aspects of themethod 700 can be executed by a wireless communication device, such as aBS 105/600, utilizing one or more components, such as the processor 602,the memory 604, the frequency compensation module 608, the transceiver610, the modem 612, the one or more antennas 616, and variouscombinations thereof. The BS 105 may be communicating with a UE 115 onan HST travelling within the range of two or more TRPs 205 on an SFN.For simplicity, the method is illustrated with reference to two TRPs205, though a greater number of TRPs 205 may be possible. Asillustrated, the method 700 includes a number of enumerated steps, butembodiments of the method 700 may include additional steps before,during, after, and in between the enumerated steps. Further, in someembodiments, one or more of the enumerated steps may be omitted orperformed in a different order.

At block 702, the BS 105 determines a first frequency pre-compensationvalue to apply to a reference signal (e.g., a TRS or a CSI-RS with TRSinformation) to be transmitted by a first TRP 205 to a UE 115. The firstfrequency pre-compensation value may be based on properties (and/orestimates of those properties) of the SFN, for example, the currentposition and/or velocity of the UE 115, or the beam(s) and/or panel(s)to be used by the first TRP 205 to transmit the TRS. The first frequencypre-compensation value may be positive (e.g., if the UE 115 is movingaway from the first TRP) or negative (e.g., if the UE 115 is movingtoward the first TRP). The first frequency pre-compensation value may bechosen arbitrarily, selected from a set (e.g., a predefined set) ofcandidate values, or from a calculation or derivation.

At block 704, the BS 105 determines a second frequency pre-compensationvalue to apply to the reference signal to be transmitted by a second TRP205 to the UE 115. The second frequency pre-compensation value may bebased on properties (and/or estimates of those properties) of the SFN,for example, the current position and/or velocity of the UE 115, or thebeam(s) and/or panel(s) to be used by the second TRP 205 to transmit thesecond TRS. The first frequency pre-compensation value may be positive(e.g., if the UE 115 is moving away from the second TRP) or negative(e.g., if the UE 115 is moving toward the second TRP), and may be thesame or different than the first frequency pre-compensation value. Thesecond frequency pre-compensation value may be chosen arbitrarily,selected from a set of candidate values, or from a calculation orderivation.

At block 706, the BS 105 transmits (e.g., in a DCI or RRC message) anindication of the first frequency pre-compensation value to the UE 115(e.g., via the first TRP 205). The value may be a raw value, or an indexinto look-up table configured at the UE 115.

At block 708, the BS 105 transmits (e.g., in a DCI or RRC message) anindication of the second frequency pre-compensation value to the UE 115(e.g., via the second TRP 205). The value may be a raw value, or anindex into look-up table configured at the UE 115. Further, the firstand second pre-compensation values may be transmitted via the TRPs 205at approximately the same time as each other, as part of the samemessage, or one after the other. Further, in some embodiments the firstand second pre-compensation values may be transmitted via respectiveTRPs 205, while in other embodiments the values may be transmitted fromone of the multiple TRPs 205.

At block 710, the BS 105 applies the first frequency pre-compensationvalue to the reference signal (or directs the first TRP 205 to apply thevalue). The first frequency pre-compensation value may increase ordecrease the frequency of the reference signal depending, respectively,on whether the UE 115 is moving away from or toward the first TRP 205.

At block 712, the BS 105 directs the first TRP 205 to transmit thereference signal (with the first frequency pre-compensation valueapplied) to the UE 115.

At block 714, the BS 105 applies the second frequency pre-compensationvalue to the reference signal (or directs the second TRP 205 to applythe value). The second frequency pre-compensation value may increase ordecrease the frequency of the reference signal depending, respectively,on whether the UE 115 is moving away from or toward the second TRP 205.The BS 105 may apply the first frequency pre-compensation value to thefirst reference and the second frequency pre-compensation value to thesecond reference signal at or near the same time as each other, orsequentially.

At block 716, the BS 105 directs the second TRP 205 to transmit thereference signal (with the second frequency pre-compensation valueapplied) to the UE 115. Further, the BS 105 may direct the first andsecond TRPs 205 to transmit their respective (pre-compensated) referencesignals to the UE at approximately the same time.

At decision block 718, the BS 105 determines whether any characteristicsof the SFN have changed. For example, the UE 115 may be in a differentposition, travelling in a different direction, or travelling at adifferent speed (either actually measured, reported, or estimated).Alternatively, one of the TRPs 205 may have adjusted the beam(s) and/orpanel(s) used to transmit their respective TRSs to the UE 115. If nochange to the SFN is detected, the method proceeds to block 720, wherethe BS 105 maintains the existing pre-compensation values. Alternately,if a change in the SFN is detected, the method returns to block 702, andthe BS 105 repeats at least some aspects of the method 700. For example,the BS 105 may repeat the entire method 700, or it may only performparts of the method 700 related to one of the two TRPs 205.

According to embodiments of the present disclosure, the BS 105 mayadditionally or alternatively perform aspects of the method 700 inrelation to other types of signals. For example, the BS 105 maydetermine frequency pre-compensation values and apply them tosynchronization signals and signals carrying system information, or toSSBs. For example, primary synchronization and/or secondarysynchronization signals may also be frequency pre-compensated on aper-beam, per-panel, or per-TRP basis to enable meaningful reception (asdiscussed with respect to the other embodiments herein). Moreover, thecoarse-level pre-adjustment may be conveyed as system information.

FIG. 8 illustrates a flow diagram of a wireless communication method 800according to some embodiments of the present disclosure. Aspects of themethod 800 can be executed by a wireless communication device, such as aUE 115/500, utilizing one or more components, such as the processor 502,the memory 504, the frequency compensation module 508, the transceiver510, the modem 512, the one or more antennas 516, and variouscombinations thereof. The UE 115 may be on an HST travelling within therange of two or more TRPs 205 on an SFN. For simplicity, the method isillustrated with reference to two TRPs 205, though a greater number ofTRPs 205 may be possible. As illustrated, the method 800 includes anumber of enumerated steps, but embodiments of the method 800 mayinclude additional steps before, during, after, and in between theenumerated steps. Further, in some embodiments, one or more of theenumerated steps may be omitted or performed in a different order.

At block 802, a UE 115 receives an indication of a first frequencypre-compensation value from a TRP 205 (e.g., a first TRP 205),originating at a BS 105. The first frequency pre-compensation value maybe an arbitrary value, or in index into a lookup table of frequencypre-compensation values configured on the UE 115, and/or from acalculation or derivation.

At block 804, the UE 115 receives an indication of a second frequencypre-compensation value originating from a TRP 205 (e.g., a second TRP205), originating at a BS 105. The indication of the second frequencypre-compensation value may be received from the same TRP 205 as thefirst frequency pre-compensation value (e.g., as sequential messages oras part of a common message) or from a different TRP 205. The secondfrequency pre-compensation value may be an arbitrary value, or in indexinto a lookup table of frequency pre-compensation values configured onthe UE 115, and/or from a calculation or derivation. Thus, the first andsecond frequency pre-compensation values may be transmitted at the sametime as each other or at different times, for use in configuring atleast a frequency tracking loop aspect of the UE 115.

At block 806, the UE 115 narrows the range of the tracking loop used toacquire the TRS based on the first pre-compensation value and the secondpre-compensation value (received at blocks 802 and 804 as discussedabove). For example, the 115 UE may adjust the frequency range it usesto search for the TRS from the first TRP 205 and the second TRP 205 (asthe TRS is received as part of the SFN, and thus the UE 115 does notknow which TRP 205 sent the TRS).

At block 808, the UE 115 receives a reference signal (e.g., a TRS)modified by the first frequency pre-compensation value. The frequency ofthe reference signal may have been adjusted upward (e.g., if the UE 115is moving away from the first TRP 205) or downward (e.g., if the UE 115is moving toward the first TRP 205).

At block 810, the UE 115 receives the reference signal (e.g., a TRS)modified by the second frequency pre-compensation value. The frequencyof the reference signal may have been adjusted upward (e.g., if the UE115 is moving away from the second TRP 205) or downward (e.g., if the UE115 is moving toward the second TRP 205). The UE 115 may receive thefirst and second reference signals (e.g., which have the same identifierand are sent on the same time/frequency resources as part of the SFN) atthe same time, such that the actions of blocks 808 and 810 occur atapproximately the same time.

At block 812, the UE 115 performs channel estimation based on the TRSreceived at blocks 808 and 810. The UE 115 may determine a channel statebased on the TRS and/or determine parameters for further communicationwith the BS 105.

At decision block 814, if there is a change in the SFN due to, forexample, a change in the UE 115's position or velocity, the UE 115 mayreport the change to the BS 105 and return to block 802 to repeataspects method 800 based on the new SFN characteristics. As anotherexample, if a different aspect of the SFN changes, for example, the beamcharacteristics used by either or both TRPs 205 to transmit thereference signal, the method 800 may return to block 802 to repeataspects of method 800. Some or all aspects of the method 800 may berepeated. For example, if only characteristics of one of the TRPs 205change, only aspects of the method related to that TRP 205 may berepeated. Alternately, if no change to the SFN occurs, the methodprogresses to block 820 where the UE will maintain the range of thetracking loop for TRSs.

In some embodiments, the UE 115 may additionally or alternativelyperform aspects of the method 800 in relation to other types of signals.For example, the UE 115 may receive synchronization signals and signalscarrying system information, and/or SSBs, with frequencypre-compensation applied. The UE 115 may also receive indications of thefrequency pre-compensation values applied to other types of signals. Forexample, primary synchronization and/or secondary synchronizationsignals may also be frequency pre-compensated on a per-beam, per-panel,or per-TRP basis to enable meaningful reception by the UE 115 (asdiscussed with respect to the other embodiments herein). Moreover, thecoarse-level pre-adjustment may be conveyed as system information.

Further aspects of the present disclosure include the following:

-   1. A method of wireless communications, comprising:

determining, by a base station, a frequency pre-compensation value for atransmission and reception point (TRP) on a single frequency network(SFN);

indicating, by the base station to a user equipment (UE), the frequencypre-compensation value via the TRP; and

applying, by the base station, the frequency pre-compensation value to asignal for transmission by the TRP to the UE.

-   2. The method of aspect 1, wherein the signal comprises a first    signal, and the frequency pre-compensation value comprises a first    frequency pre-compensation value associated with a first    Transmission Configuration Indicator (TCI) state, further    comprising:

determining, by the base station, a second frequency pre-compensationvalue for the TRP associated with a second TCI state; and

applying, by the base station, the second frequency pre-compensationvalue to a second signal for transmission by the TRP to the UE.

-   3. The method of aspect 1, wherein the TRP comprises a first TRP and    the frequency pre-compensation value comprises a first frequency    pre-compensation value, the method further comprising:

determining, by the base station, a second frequency pre-compensationvalue for a second TRP on the SFN for use with the signal;

indicating, by the base station, the second frequency pre-compensationvalue to the UE via the first TRP or the second TRP; and

applying, by the base station, the second frequency pre-compensationvalue to the signal for transmission by the second TRP to the UE.

-   4. The method of any of aspects 1-3, wherein an indication of the    frequency pre-compensation value is included, by the base station,    in a downlink control information (DCI) message.-   5. The method of any of aspects 1-4, wherein the frequency    pre-compensation value is determined based on a frequency    measurement of a reference signal from the UE.-   6. The method of any of aspects 1-4, wherein the frequency    pre-compensation value is determined based on a frequency    measurement of a reference signal from the base station.-   7. The method of any of aspects 1-6, further comprising:

updating, by the base station, the frequency pre-compensation value inresponse to a change in the SFN; and

indicating, by the base station to the UE, the updated frequencypre-compensation value via the TRP.

-   8. A method of wireless communications, comprising:

receiving, by a user equipment (UE) on a single frequency network (SFN),an indication of a frequency pre-compensation value for use by atransmission and reception point (TRP);

receiving, by the UE, a signal modified by the frequencypre-compensation value;

narrowing, by the UE, a range of a tracking loop based on the indicatedfrequency pre-compensation value; and

performing, by the UE, channel estimation of the signal based on thenarrowed tracking loop.

-   9. The method of aspect 8, wherein the signal comprises a first    signal, and the indication of a frequency pre-compensation value    comprises a first indication of a first frequency pre-compensation    value associated with a first Transmission Configuration Indicator    (TCI) state, further comprising:

receiving, by the UE from the TRP, a second indication of a secondfrequency pre-compensation value associated with a second TCI state foruse by the TRP; and

receiving, by the UE from the TRP, a second signal modified by thesecond frequency pre-compensation value;

wherein the narrowing is further based on the second indicated frequencypre-compensation value.

-   10. The method of aspect 8, wherein the TRP comprises a first TRP,    the receiving the signal further comprising receiving the signal    from a second TRP as well as the first TRP.-   11. The method of aspect 10, wherein the frequency pre-compensation    value comprises a first frequency pre-compensation value, the    receiving the frequency pre-compensation value further comprising:

receiving, by the UE from a second TRP, an indication of a secondfrequency pre-compensation value for use by the second TRP.

-   12. The method of either aspect 9 or 11, wherein the narrowing is    based on the second frequency pre-compensation value as well as the    first frequency pre-compensation value.-   13. The method of any of aspects 8-12, wherein the indication is    part of a downlink control information (DCI) message.-   14. The method of any of aspects 8-13, wherein the frequency    pre-compensation value is determined based on a frequency    measurement of a reference signal from the UE.-   15. The method of any of aspects 8-13, wherein the frequency    pre-compensation value is determined based on a frequency    measurement of a reference signal from the TRP.-   16. A base station, comprising:

a memory;

a transceiver; and

a processor coupled with the memory and the transceiver and configured,when executing instructions stored on the memory, to cause the basestation to:

-   -   determine a frequency pre-compensation value for a transmission        and reception point (TRP) on a single frequency network (SFN);    -   indicate to a user equipment (UE) the frequency pre-compensation        value via the TRP; and    -   apply the frequency pre-compensation value to a signal for        transmission by the TRP to the UE.

-   17. The base station of aspect 16, wherein the signal comprises a    first signal, and the frequency pre-compensation value comprises a    first frequency pre-compensation value associated with a first    Transmission Configuration Indicator (TCI) state, the transceiver    and the processor further configured to:

determine a second frequency pre-compensation value for the TRPassociated with a second TCI state; and

apply the second frequency pre-compensation value to a second signal fortransmission by the TRP to the UE.

-   18. The base station of aspect 16, wherein the TRP comprises a first    TRP, the frequency pre-compensation value comprises a first    frequency pre-compensation value, and the transceiver and the    processor re further configured to:

determine a second frequency pre-compensation value for a second TRP onthe SFN for use with the signal;

indicate the second frequency pre-compensation value to the UE via thefirst TRP or the second TRP; and

apply the second frequency pre-compensation value to the signal fortransmission by the second TRP to the UE.

-   19. The base station of any of aspects 16-18, wherein the    transceiver and the processor are configured to indicate the    frequency pre-compensation value by:

including an indication of the frequency pre-compensation value in adownlink control information (DCI) message.

-   20. The base station of any of aspects 16-19, wherein the    transceiver and the processor are configured to determine the    frequency pre-compensation value by:

estimating the frequency pre-compensation value based on a measurement,by the TRP, of a reference signal from the UE.

-   21. The base station of any of aspects 16-19, wherein the    transceiver and the processor are configured to determine the    frequency pre-compensation value by:

estimating the frequency pre-compensation value based on a measurement,by the UE, of a reference signal from the base station.

-   22. The base station of any of aspects 16-21, wherein the    transceiver and the processor are further configured to:

update the frequency pre-compensation value in response to a change inthe SFN; and indicate to the UE the updated frequency pre-compensationvalue via the TRP.

-   23. A user equipment (UE), comprising:

a memory;

a transceiver; and

a processor coupled with the memory and the transceiver and configured,when executing instructions stored on the memory, to cause the UE to:

-   -   receive on a single frequency network (SFN) an indication of a        frequency pre-compensation value for use by a transmission and        reception point (TRP);    -   receive a signal modified by the frequency pre-compensation        value; narrow range of a tracking loop based on the indicated        frequency pre-compensation value; and    -   perform channel estimation of the signal based on the narrowed        tracking loop.

-   24. The UE of aspect 23, wherein the signal comprises a first    signal, and the indication of a frequency pre-compensation value    comprises a first indication of a first frequency pre-compensation    value associated with a first Transmission Configuration Indicator    (TCI) state, the transceiver and the processor further configured    to:

receive, from the TRP, a second indication of a second frequencypre-compensation value associated with a second TCI state for use by theTRP; and

receive, from the TRP, a second signal modified by the second frequencypre-compensation value; and

-   -   narrow range of the tracking loop further based on the second        indicated frequency pre-compensation value.

-   25. The UE of aspect 23, wherein the TRP comprises a first TRP, and    the transceiver and the processor are configured to receive the    signal by receiving the signal from a second TRP as well as the    first TRP.

-   26. The UE of aspect 25, wherein the frequency pre-compensation    value comprises a first frequency pre-compensation value, and the    transceiver and the processor are further configured to receive an    indication of a second frequency pre-compensation value from the    second TRP.

-   27. The UE of either aspect 24 or 26, wherein the narrowing is based    on the second frequency pre-compensation value as well as the first    frequency pre-compensation value.

-   28. The UE of any of aspects 23-27, wherein the indication is part    of a downlink control information (DCI) message.

-   29. The UE of any of aspects 23-28, wherein the frequency    pre-compensation value is determined based on a frequency    measurement, by the TRP, of a reference signal from the UE.

-   30. The UE of any of aspects 23-28, wherein the frequency    pre-compensation value is determined based on a frequency    measurement, by the UE, of a reference signal from the TRP.

-   31. A method of wireless communications, comprising:

determining, by a base station, a frequency pre-compensation value for atransmission and reception point (TRP) on a single frequency network(SFN);

indicating, by the base station to a user equipment (UE), the frequencypre-compensation value via the TRP;

applying, by the base station, the frequency pre-compensation value to asignal; and

directing, by the base station, the TRP to transmit the signal with theapplied pre-compensation value to the UE.

Information and signals may be represented using any of a variety ofdifferent technologies and techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips that may bereferenced throughout the above description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a DSP, an ASIC, an FPGA or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations. Also, as used herein, including in the claims, “or” as usedin a list of items (for example, a list of items prefaced by a phrasesuch as “at least one of” or “one or more of”) indicates an inclusivelist such that, for example, a list of [at least one of A, B, or C]means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

As those of some skill in this art will by now appreciate and dependingon the particular application at hand, many modifications, substitutionsand variations can be made in and to the materials, apparatus,configurations and methods of use of the devices of the presentdisclosure without departing from the spirit and scope thereof. In lightof this, the scope of the present disclosure should not be limited tothat of the particular embodiments illustrated and described herein, asthey are merely by way of some examples thereof, but rather, should befully commensurate with that of the claims appended hereafter and theirfunctional equivalents.

What is claimed is:
 1. A method of wireless communications, comprising:determining, by a base station, a frequency pre-compensation value for atransmission and reception point (TRP) on a single frequency network(SFN); indicating, by the base station to a user equipment (UE), thefrequency pre-compensation value via the TRP; and applying, by the basestation, the frequency pre-compensation value to a signal fortransmission by the TRP to the UE.
 2. The method of claim 1, wherein thesignal comprises a first signal, and the frequency pre-compensationvalue comprises a first frequency pre-compensation value associated witha first Transmission Configuration Indicator (TCI) state, furthercomprising: determining, by the base station, a second frequencypre-compensation value for the TRP associated with a second TCI state;and applying, by the base station, the second frequency pre-compensationvalue to a second signal for transmission by the TRP to the UE.
 3. Themethod of claim 1, wherein the TRP comprises a first TRP and thefrequency pre-compensation value comprises a first frequencypre-compensation value, the method further comprising: determining, bythe base station, a second frequency pre-compensation value for a secondTRP on the SFN for use with the signal; indicating, by the base station,the second frequency pre-compensation value to the UE via the first TRPor the second TRP; and applying, by the base station, the secondfrequency pre-compensation value to the signal for transmission by thesecond TRP to the UE.
 4. The method of claim 1, wherein an indication ofthe frequency pre-compensation value is included, by the base station,in a downlink control information (DCI) message.
 5. The method of claim1, wherein the frequency pre-compensation value is determined based on afrequency measurement of a reference signal from the UE.
 6. The methodof claim 1, wherein the frequency pre-compensation value is determinedbased on a frequency measurement of a reference signal from the basestation.
 7. The method of claim 1, further comprising: updating, by thebase station, the frequency pre-compensation value in response to achange in the SFN; and indicating, by the base station to the UE, theupdated frequency pre-compensation value via the TRP.
 8. A method ofwireless communications, comprising: receiving, by a user equipment (UE)on a single frequency network (SFN), an indication of a frequencypre-compensation value for used by a transmission and reception point(TRP); receiving, by the UE, a signal modified by the frequencypre-compensation value; narrowing, by the UE, a range of a tracking loopbased on the indicated frequency pre-compensation value; and performing,by the UE, channel estimation of the signal based on the narrowedtracking loop.
 9. The method of claim 8, wherein the signal comprises afirst signal, and the indication of a frequency pre-compensation valuecomprises a first indication of a first frequency pre-compensation valueassociated with a first Transmission Configuration Indicator (TCI)state, further comprising: receiving, by the UE from the TRP, a secondindication of a second frequency pre-compensation value associated witha second TCI state for use by the TRP; and receiving, by the UE from theTRP, a second signal modified by the second frequency pre-compensationvalue; wherein the narrowing is further based on the second indicatedfrequency pre-compensation value.
 10. The method of claim 8, wherein theTRP comprises a first TRP, the receiving the signal further comprisingreceiving the signal from a second TRP as well as the first TRP.
 11. Themethod of claim 10, wherein the frequency pre-compensation valuecomprises a first frequency pre-compensation value, the receiving thefrequency pre-compensation value further comprising: receiving, by theUE from a second TRP, an indication of a second frequencypre-compensation value for use by the second TRP.
 12. The method ofclaim 11, wherein the narrowing is based on the second frequencypre-compensation value as well as the first frequency pre-compensationvalue.
 13. The method of claim 8, wherein the indication is part of adownlink control information (DCI) message.
 14. The method of claim 8,wherein the frequency pre-compensation value is determined based on afrequency measurement of a reference signal from the UE.
 15. The methodof claim 8, wherein the frequency pre-compensation value is determinedbased on a frequency measurement of a reference signal from the TRP. 16.A base station, comprising: a memory; a transceiver; and a processorcoupled with the memory and the transceiver and configured, whenexecuting instructions stored on the memory, to cause the base stationto: determine a frequency pre-compensation value for a transmission andreception point (TRP) on a single frequency network (SFN); indicate to auser equipment (UE) the frequency pre-compensation value via the TRP;and apply the frequency pre-compensation value to a signal fortransmission by the TRP to the UE.
 17. The base station of claim 16,wherein the signal comprises a first signal, and the frequencypre-compensation value comprises a first frequency pre-compensationvalue associated with a first Transmission Configuration Indicator (TCI)state, the transceiver and the processor further configured to:determine a second frequency pre-compensation value for the TRPassociated with a second TCI state; and apply the second frequencypre-compensation value to a second signal for transmission by the TRP tothe UE.
 18. The base station of claim 16, wherein the TRP comprises afirst TRP, the frequency pre-compensation value comprises a firstfrequency pre-compensation value, and the transceiver and the processorare further configured to: determine a second frequency pre-compensationvalue for a second TRP on the SFN for use with the signal; indicate thesecond frequency pre-compensation value to the UE via the first TRP orthe second TRP; and apply the second frequency pre-compensation value tothe signal for transmission by the second TRP to the UE.
 19. The basestation of claim 16, wherein the transceiver and the processor areconfigured to indicate the frequency pre-compensation value by:including an indication of the frequency pre-compensation value in adownlink control information (DCI) message.
 20. The base station ofclaim 16, wherein the transceiver and the processor are configured todetermine the frequency pre-compensation value by: estimating thefrequency pre-compensation value based on a measurement, by the TRP, ofa reference signal from the UE.
 21. The base station of claim 16,wherein the transceiver and the processor are configured to determinethe frequency pre-compensation value by: estimating the frequencypre-compensation value based on a measurement, by the UE, of a referencesignal from the base station.
 22. The base station of claim 16, whereinthe transceiver and the processor are further configured to: update thefrequency pre-compensation value in response to a change in the SFN; andindicate to the UE the updated frequency pre-compensation value via theTRP.
 23. A user equipment (UE), comprising: a memory; a transceiver; anda processor coupled with the memory and the transceiver and configured,when executing instructions stored on the memory, to cause the UE to:receive on a single frequency network (SFN) an indication of a frequencypre-compensation value for use by a transmission and reception point(TRP); receive a signal modified by the frequency pre-compensationvalue; narrow range of a tracking loop based on the indicated frequencypre-compensation value; and perform channel estimation of the signalbased on the narrowed tracking loop.
 24. The UE of claim 23, wherein thesignal comprises a first signal, and the indication of a frequencypre-compensation value comprises a first indication of a first frequencypre-compensation value associated with a first TransmissionConfiguration Indicator (TCI) state, the transceiver and the processorfurther configured to: receive, from the TRP, a second indication of asecond frequency pre-compensation value associated with a second TCIstate for use by the TRP; and receive, from the TRP, a second signalmodified by the second frequency pre-compensation value; and narrowrange of the tracking loop further based on the second indicatedfrequency pre-compensation value.
 25. The UE of claim 23, wherein theTRP comprises a first TRP, and the transceiver and the processor areconfigured to receive the signal by receiving the signal from a secondTRP as well as the first TRP.
 26. The UE of claim 25, wherein thefrequency pre-compensation value comprises a first frequencypre-compensation value, and the transceiver and the processor arefurther configured to receive an indication of a second frequencypre-compensation value from the second TRP.
 27. The UE of claim 26,wherein the narrowing is based on the second frequency pre-compensationvalue as well as the first frequency pre-compensation value.
 28. The UEof claim 23, wherein the indication is part of a downlink controlinformation (DCI) message.
 29. The UE of claim 23, wherein the frequencypre-compensation value is determined based on a frequency measurement,by the TRP, of a reference signal from the UE.
 30. The UE of claim 23,wherein the frequency pre-compensation value is determined based on afrequency measurement, by the UE, of a reference signal from the TRP.